National Institute of Standards and Technology
Computational Chemistry Comparison and Benchmark DataBase
Release 17bSeptember 2015
NIST Standard Reference Database 101
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III.D.11.

Calculated Proton Affinity

Name Species   Species Name
Carbon diatomic C2 C2H+ Ethynyl cation

Bonding changes

Bond type H-C gained 1
Proton Affinities (kJ/mol)
Proton Affinities in kJ/mol
Methods with predefined basis sets
composite G2 389
G3 383
G3B3 640
G4 393
CBS-Q 386

Proton Affinities in kJ/mol
Methods with standard basis sets
STO-3G 3-21G 3-21G* 6-31G 6-31G* 6-31G** 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) TZVP cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ
hartree fock HF 488 353 353 358 345 351 340 337 345 349 352 330 347 348 326 346 348
density functional LSDA 519 401 401 409 395 400 386 386 394 401   383 397   379 396  
SVWN   401         386       603            
BLYP 493 393 393 401 671 393 376 380 387 393   374 389        
B1B95 496 387 387 396 384 390 377 376 384 391   371 388 389 374 387 678
B3LYP 498 392 392 399 350 390 376 378 385 390 387 371 387 389 366 386 388
B3LYPultrafine   392     384 390 376 378       371 387     386  
B3PW91 497 388 388 397 383 388 377 377 385 389   371 387        
mPW1PW91 496 385 385 394 380 385 374 375 382 386   368 384        
M06-2X     1830   397                        
PBEPBE 495 388 388 398 385 391 376 378 386 390   374 387 389     388
PBE1PBE         378                        
HSEh1PBE   385     379   487           382        
TPSSh         376   370     643     380        
wB97X-D     782   808       807       812     812  
STO-3G 3-21G 3-21G* 6-31G 6-31G* 6-31G** 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) TZVP cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ
Moller Plesset perturbation MP2 553 392 392 395 380 396 382 368 386 396 393 372 392   364 390 635
MP2=FULL 553 392 392 395 382 399 385 370 388 400   373 403     403 640
MP3         656                        
MP3=FULL         375   380                    
MP4   405     385       391       395        
B2PLYP         385               389        
Configuration interaction CID   409 409 410 379     368                  
CISD   409 409 408 379     368                  
STO-3G 3-21G 3-21G* 6-31G 6-31G* 6-31G** 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) TZVP cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ
Quadratic configuration interaction QCISD   422 422 426 401 417 404 387 405 412   392 408        
QCISD(T)         419             414 421   406 419  
Coupled Cluster CCD     435 433 399 415 403 385 403 410   390 407   382 406  
CCSD         399                        
CCSD(T)         423             418 424   409 422  
CCSD(T)=FULL         424                        
STO-3G 3-21G 3-21G* 6-31G 6-31G* 6-31G** 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) TZVP cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ

Proton Affinities in kJ/mol
Methods with effective core potentials (select basis sets)
CEP-31G CEP-31G* CEP-121G CEP-121G* LANL2DZ SDD
hartree fock HF 309 296 328 321 346 346
density functional B3LYP 345 544 357 350 381 381
Moller Plesset perturbation MP2 350 341 357 348 375 374
For descriptions of the methods (AM1, HF, MP2, ...) and basis sets (3-21G, 3-21G*, 6-31G, ...) see the glossary in section I.C. Predefined means the basis set used is determined by the method.